So - Circuits: This is a bit of an extension on a project for my Introduction to Electronics course. The original design was a simple, twelve-note Arduino-based polyphonic synthesizer that used an Altera FPGA demo board to MUX the inputs together into a four-bit number.
Along the bottom you can see a row of twelve SPDT momentary push button switches wired up as active-high inputs to the Freeduino board on the left. Switches one through six are wired up to the analog inputs; which can actually be used as digital inputs through the "digitalRead" command using the pin numbers 14-19. The remaining six switches are connected to digital inputs two through seven, with pins ten through thirteen constituting the "data bus" between the two Arduinos.
The Arduino on the left is running David's (my instructor) original synthesizer code. The software decodes the four-bit binary number it sees from the "keyboard" and plays the corresponding note through a DAC over the SPI bus. The pot dangling off the right side of the board is used to fine-tune the synthesizer pitch, and the speaker in the middle-right produces rich, high-fidelity audio comparable to the output of singing greeting cards and the score of most video games from the 1980s'.
I'm still hacking away at the firmware: I'm having trouble figuring out how to encode the number read from the keyboard as a binary number correctly. Perhaps it a solution will jump out at me tomorrow morning...
Oh - and one last thing:
"I ALWAYS have coffee when I watch radar. Everybody knows that!"